1. Field of the Invention
The invention relates to a fluid coupling with a damping mechanism for a bimetallic spiral spring, which coupling may be used in an automobile.
2. Description of the Related Art
In the conventional coupling with a damping mechanism for a bimetal spring in FIGS. 12 and 13, a casing 3 is supported on a drive shaft 1 by a bearing 4, and a cover 6 is formed to the casing 3 to form a chamber therebetween. An O-ring 7 is set between the contact faces of the casing 3 and a cover 6. A partition plate 8 is fixed to the cover 6 in order to partition the chamber into a reservoir 10 and an operation chamber 9. A rotor 2 is fixed to the drive shaft 1 and is disposed in the operation chamber 9. On both opposing faces of the casing 3 and the rotor 2 are formed labyrinth grooves 5. The partition plate 8 has a passage 11 so that the fluid in the reservoir 10 can enter the operation chamber 9.
A rod 12 is supported by the cover 6. On one end of the rod 12 is fixed a valve plate 14, and on the other end of the rod is fixed an inner end 13a of a bimetal spring 13. The outer end 19 of the bimetal spring 13 has a bent portion and is fixed to a boss 20 formed on the cover 6. The bimetal spring 13 responds to the temperature of the atmosphere behind a radiator (not shown) so that the valve plate 14 moves to open and close the passage 11.
A plate 15 is fixed to the cover 6 by screws 15a, and has projection 16 with a rubber block 17 adhered thereto and contacting the bimetal spring 13. The plate 15 has holes 18, so that the bimetal spring 13 can respond to the temperature of the air flowing through the holes 18.
The bimetal spring 13 vibrates in resonance with the vibrations of the engine, suspension, etc. and it is possible for the bimetal spring 13 to break, particularly at the bent point A in FIG. 13, unless a damping mechanism such as that comprising the rubber block 17 is provided. However, when the plate 15 with the rubber block 17 is attached to the cover 6, it is difficult to know the degree of contact of the rubber block 17 with the bimetal spring 13, because the contact portions of the rubber block 17 and the bimetal spring 13 are obstructed by the plate 15. Therefore, excessive adjustment time is necessary. Further the plate 15 reduces the temperature responsiveness of the bimetal spring 13, in spite of the holes 18, because a sufficient air-flow to the bimetal spring 13 cannot be assured by the holes 18.